1. Field of the Invention
The present invention relates to pattern devices used for displaying images such as for advertising, and particularly to an electrically illuminated pattern device.
2. Description of Prior Art
A conventional pattern device, such as a registration mark of a billboard or a vehicle, cannot illuminate by itself. If the image of the pattern device is to be clearly seen at night, it must be illuminated by an external source. However, external illumination has various inherent limitations, including the angle of illumination, the brightness of the source, and the reflective ratio of the pattern device. These limitations frequently result in the pattern device being unevenly illuminated. Furthermore, the brightness and overall display of the pattern device may be unsatisfactory.
Generally, to solve the above-described problems, an active light source is arranged at the back of the pattern device. A pattern device having an active light source arranged at the back thereof is known as an illuminated pattern device.
A conventional illuminated pattern device is represented in FIGS. 6 and 7. The illuminated pattern device 1 includes a pattern body 12, a frame 16 arranged around a periphery of the pattern body 12, and a dot light source 101 arranged at the back of the pattern body 12. The pattern body 12 is elliptical, and includes a pattern 121, a top surface 17, a cavity 18 and a bottom surface 19. The pattern 121 defines a projection surface (not labeled) on the bottom surface 19. The cavity 18 is defined between the top surface 17 and the bottom surface 19. The dot light source 101 is a light emitting diode (LED), and is secured in the cavity 18. In particular, the dot light source 101 is arranged at a center of the projection surface defined on the bottom surface 19.
Because the dot light source 101 is arranged at a center of the projection surface, the distribution of the light energy from the dot light source 101 is uneven. For example, a central circular area 100 on the pattern body 12 receives much more light energy from the dot light source 101 than other portions of the pattern body 12. Accordingly, a brightness of the pattern 121 is not uniform. The result is that the overall pattern 121 cannot be clearly seen at night.